The lens is NA 0.8 so usually a step size close to 0.0005 mm (0.5 microns) will be OK with a little marginal.

I was trying to do a depth map where the dents could be seen. To do this I had to have smaller than normal steps. In this case I used 0.0001 mm (0.1 micron), so 319 pictures covered the distance of approx. 0.032 mm (32 microns).

I was interested in trying to have a clean black background. Tried some different options. For this BW-picture I used a Nikon plan apo 40x BD 210 mm lens, dark field, and green light (GIF-filter). The green light helped even though this was an APO-lens.

Beautiful monochrome shot. If you want to push this farther, you might want to use violet lasers and a cooled monochrome camera.....you'd achieve 20% more resolution and get smooth backgrounds with no thermal noise._________________Lou Jost
www.ecomingafoundation.wordpress.comwww.loujost.com